We propose to develop transposition of Tn3 in vitro. We are using two assays for this process. One is a bioassay and is very sensitive; the other assay involves gel electrophoresis and has the advantage of potentially identifying intermediates in transposition. We will purify the Tn3 transposase by an independent method and add it to the extracts. If we succeed in getting in vitro transposition we will purify the requisite enzymes. During this work we have discovered an E. coli activity which oligomerizes circular DNA and we will purify and characterize this enzyme.